Soldering is a method for connecting and bonding components to provide secure electrical connections in the electronics industry. Soldering can be roughly classified into two categories, namely, mass soldering (batch soldering) and manual soldering. Mass soldering includes wave or flow soldering wherein electrical elements or components are mounted on a printed circuit board and then the printed circuit board is passed over a molten solder bath in a manner that allows selective contact with the solder. Mass soldering further includes reflow soldering (SMT) wherein solder particles and flux are mixed with a binder or additive to form a solder paste. The solder paste is printed on the circuit board, and the elements are then mounted on the circuit board and heated so as to solder them. Both of these methods allow simultaneous soldering of multiple points.
Manual soldering using an electric soldering iron allows an individual user to perform soldering operations. Manual soldering can be used following the mass soldering methods described above, to repair localized defective soldering, or to solder parts which cannot be soldered with the mass soldering methods.
Conventional soldering iron tips for electric soldering irons are made of copper or copper alloys and their forward ends are iron plated to a thickness of from thirty to fifty micrometers up to five hundred to eight hundred micrometers, in order to prevent solder corrosion of the copper. This iron-plated area is then coated or wetted with solder, and soldering operations are performed therewith.
In the past it was common for the principal components of solder to be tin and lead (Sn—Pb solders of which Sn—Pb eutectic solder is representative thereof). However, in recent years due to environmental concerns, lead is less commonly used and so-called lead-free solders have been more frequently used. Examples of lead-free solders are Sn—Cu solders, Sn—Ag solders, and Sn—Ag—Cu solders.
As compared to Sn—Pb solders, it is more difficult to achieve good solder joints with lead-free solders, due to inferior solder wetting and the difficulty of solder spreading. The primary causes of inferior solder wetting include the facts that the melting points are 20° C. to 45° C. higher than Sn—Pb solders and the iron tips of the soldering irons are more readily oxidized. Consequently, soldering work using manual soldering methods has suffered. Soldering defects are more likely to result with manual soldering which uses lead-free solder and thereby more frequent repairs are required. The present applicants have invented technology for improving soldering performance while maintaining substantially the same degree of solder corrosion durability of the soldering iron tip as prior iron plated soldering iron tips experienced with leaded solder. This is described in patent document A JP-2000-317629, entitled “Soldering Iron Tip” and filed on May 10, 1999. As described in this document, instead of conventional iron plating, an Fe—Ni alloy plating is used at the forward end of the soldering iron tip, or an Fe—Ni alloy covering member (a bulk material) is provided to improve soldering performance.
Furthermore, soldering related operations include desoldering wherein (electric) solder suction devices are used to remove undesired solder. These devices have a suction nozzle that is heated such as by a built-in heater, and the end of the heated suction nozzle is contacted with the solder to thereby melt it. The molten solder is suctioned into the interior of the desoldering tool through an opening at the end of the suction nozzle. The suctioning is performed by a vacuum pump or the like, and the molten solder is stored in a tank (or a capsule) having a filter provided in the suction passageway thereto.
With respect to the function of melting solder when the heated tip contacts the solder, and the requirement of good solder wetting in order to maintain good heat transfer characteristics, the suction nozzle of the electric solder suction device is similar to the soldering iron tip of an electric soldering iron, and similar iron plating is typically used at the forward end thereof. Similar to the soldering iron tip of the electric soldering iron, desoldering tip corrosion is to be prevented and solder wettability is to be maintained, even when using lead-free solder.
The tips of soldering irons wear out quickly, and therefore most industrial soldering irons are designed so that the tip can be replaced as needed instead of always replacing the entire soldering iron when the tip erodes or otherwise wears out. There are basically three different types of replaceable tip designs in the prior art, as discussed below.
The first type is one where an elongate tip is releasably held inside an elongate heater. An example thereof is disclosed in U.S. Pat. No. 5,422,457 (Tang et al.). (This patent and all other patents, publications and applications mentioned anywhere in this disclosure are hereby incorporated by reference in their entireties.)
The second type is shown, for example, in U.S. Pat. No. 5,248,076 (Eisele et al.). It includes a tip which is fitted over a temperature sensor and heater extending out from the soldering iron body.
The third type is shown in U.S. Pat. No. 6,054,678 (Miyazaki) and U.S. Pat. No. 6,215,104 (Kurpiela et al.). The constructions shown therein are an entire heating unit including the tip sensor and heater, which are built as a one-piece device for better heat transfer than that of the second type. The entire unit is replaced when the tip, which can be a copper tip with an iron plating, becomes worn out. The unit can be pressed into a sleeve or pushed into a socket; and in other words, it is a composite tip having a built-in heater.
The soldering tips of the first two types have structures where the tips are either positioned into an opening in a heater as in the first type, or positioned onto a heater as in the second type. The heat for the soldering operation is conducted from the heater through the tip to the work area. The structures of these two types have a clearance or gap between the heater and the tip. Thus, the heat conduction is less than that of the soldering iron of the third type, which has a tip heater composite structure. Disadvantageously, the replaceable composite heater assembly of the third type has a high operating cost, because when the tip wears out the heater and sensor units must also be replaced.
Examples of soldering irons are U.S. Pat. No. 1,667,618 (Abbott), U.S. Pat. No. 29,039 (Patee), JP 2000-288723 (Matsuzawa), U.S. Pat. No. 4,568,819 (Stacconi), U.S. Pat. No. 6,019,270 (Boll et al.), U.S. 2004/0226981 (Nagase et al.), U.S. Pat. No. 6,793,114 (Dunham et al.), U.S. Pat. No. 6,513,697 (Sines et al.), U.S. Publication No. 2005-0092729 (Konishi et al.), Japanese Utility Model 2080187 published Nov. 30, 1994, U.S. Publication 2004/0222206 (Nagase, et al.), and U.S. Publication 2005/0011876 (Uetani, et al.).